Components are the parts of a geometric object such as points, edges, and polygons.
Individual components are referenced using an number called an index. For example, the following expression refers to the
point at index number 3 on the cube "aCube":
"aCube.pnt[3]"
Component indexes start at 0, so the first point is:
"aCube.pnt[0]"
For this reason, it is easier to think of aCube.pnt[3] as point number 3 instead of as the fourth point.
Geometric components such as points are indexed from 0 to LAST.
Examples:
Expression

What it indicates

"Cone.pnt[3,6,8]"

Points 3, 6 and 8 on an object named "Cone"

"Cone.pnt[38,10]"

Points 3 to 8 and 10

"Cone.pnt[*]"

All the points on the object (equivalent to Cone.point[0LAST])

"cube.poly[1]"

The polygon

"cube.edge[13,6,LAST]"

Points 1 to 3, 6, and the last point

Here's some examples for a nurbs surface:
Expression

What it indicates

"sphere.pnt[(2,4)]"

Point (at u=2 and v=4)

"sphere.pnt[(4,2),(4,6)]"

Two points

"sphere.isopnt[(0.621,0.682)]"

An isopoint

"sphere.knotcrvu[2,3]"

A knot curve

"sphere.isolineu[0.594]"

An isoline

"sphere.bndry[*]"

A boundary

"sphere.subsrf[0]"

A subsurface

"sphere.knot[(7,2)]"

A knot
